## Search found 102 matches

Fri Mar 12, 2021 2:40 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: cell diagram from lecture
Replies: 3
Views: 13

### cell diagram from lecture

Hi! I had a question about the cell diagram from Dr. Lavelle's review session today. Would you need to change the AgBr to Ag+? I thought the species closest to the salt bridge needs to be aqueous. Thanks!
Fri Mar 12, 2021 12:34 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: catalyst vs temp increase
Replies: 2
Views: 9

### catalyst vs temp increase

Hi! I was wondering if a catalyst and an increase in temperature have the same effect on a reaction? Will they both increase the rate constants? Thanks!
Thu Mar 11, 2021 10:48 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: textbook 7D.5
Replies: 4
Views: 37

### textbook 7D.5

Hi! For this problem, I saw in the solution manual that there was a -.59 at the end of the equation. I was wondering where that is coming from? Thanks!
Wed Mar 10, 2021 11:24 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: textbook 6L.3
Replies: 1
Views: 17

### textbook 6L.3

Hi! I was wondering if someone could explain part c? I wasn't sure how to balance this one. Thanks!
Wed Mar 10, 2021 1:55 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: pt in cell diagram
Replies: 2
Views: 20

### pt in cell diagram

Hi! I was wondering how you know when to include platinum in the cell diagram? Thanks!
Sat Mar 06, 2021 8:36 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: molecularity and rate laws
Replies: 4
Views: 15

### molecularity and rate laws

Hi! I was a little confused on how the molecularity of each step relates to the rate law? Also, how do you combine the rate laws of each step to get the overall rate law? Do you just add them together or do any parts get cancelled out if there is an intermediate included? Thanks!
Sat Mar 06, 2021 8:34 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: intermediates
Replies: 11
Views: 35

### intermediates

Hi! I was wondering how you know what the intermediates are? Why are they not included in the rate law? Is the only way to identify the intermediates through the reaction mechanism? Thanks!
Fri Mar 05, 2021 1:02 pm
Forum: General Rate Laws
Topic: rate law components
Replies: 7
Views: 34

### rate law components

Hi! I was wondering why the rate law for a reaction does not consider the concentration of the products? Thanks!
Thu Mar 04, 2021 10:18 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Textbook 6.53
Replies: 1
Views: 21

### Textbook 6.53

Hi! I was wondering for part b, why would dilution of the anode concentration increase the cell potential? Thanks!
Thu Mar 04, 2021 10:15 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: cell notation
Replies: 12
Views: 64

### cell notation

Hi! I was wondering if the cathode is always the species on the right of the cell notation? Is that the species always being reduced? Thanks!
Sat Feb 27, 2021 10:16 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: sapling week 7/8 #12
Replies: 3
Views: 35

### sapling week 7/8 #12

Hi! I was wondering how you find the number of electrons transferred to use the equation ΔG=-nFE°? Thanks!
Fri Feb 26, 2021 8:05 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: oxidizing agent and reduction potential
Replies: 2
Views: 21

### oxidizing agent and reduction potential

Hi! I was wondering what the correlation is between an atom's reduction potential value and how strong of an oxidizing agent it is? If the reduction potential is high, does this mean it is a strong oxidizing agent? Thanks!
Fri Feb 26, 2021 1:38 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: reaction energy barrier
Replies: 10
Views: 56

### reaction energy barrier

Hi! I was wondering how a reaction can have an energy barrier if it is spontaneous? Wouldn't this mean that there needs to be an inflow of energy for the reaction to take place, making it non spontaneous? If someone could explain the energy barrier related to spontaneity that would be great, thanks!
Fri Feb 26, 2021 1:36 pm
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Kinetic stability
Replies: 14
Views: 102

### Kinetic stability

Hi! Dr. Lavelle mentioned in his example with Carbon as graphite and diamond that the diamond form is kinetically stable. I was wondering what kinetic stability is? Thanks!
Thu Feb 25, 2021 9:41 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: concentration cell
Replies: 3
Views: 36

### concentration cell

Hi! I was having trouble understanding what a concentration cell is. If someone could explain this, that would be great! Thanks!
Sun Feb 21, 2021 10:35 am
Forum: Balancing Redox Reactions
Topic: salt bridge
Replies: 19
Views: 73

### salt bridge

Hi! I was wondering what exactly was the purpose of the salt bridge that Dr. Lavelle mentioned in the electrode experiment? How does it help conduct the flow of electrons? Thanks!
Thu Feb 18, 2021 6:34 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Replies: 6
Views: 36

Hi! I was wondering how you find the final temperature of an adiabatic reaction? Is there a temperature change since q=0 in an adiabatic reaction? Thanks!
Wed Feb 17, 2021 11:35 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Textbook Problem 4B.3
Replies: 2
Views: 23

### Re: Textbook Problem 4B.3

Hi! If you rearrange the equation ΔU= q+w to solve for work, you get w=ΔU-q. If you subtract the amount of heat supplied from the change in internal energy, you get the work. Since the value for work would be positive in this case, work is done on the system. Hope this helps!
Wed Feb 17, 2021 11:27 pm
Forum: Balancing Redox Reactions
Topic: coefficients for oxidation number
Replies: 22
Views: 106

### coefficients for oxidation number

Hi! I was wondering if you have to consider the coefficient of a molecule in a chemical reaction when identifying its oxidation number? If so, do you multiply the atom's oxidation number by the coefficient? Thanks!
Wed Feb 17, 2021 11:25 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: driving force of dissolution
Replies: 1
Views: 25

### driving force of dissolution

Hi! I was wondering how you know what the driving force of a reaction is? In part e of this question, it asks what the driving force of dissolution is and I was not sure how to find this. Thanks!
Sat Feb 13, 2021 12:59 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: sapling week 5/6 #7
Replies: 5
Views: 72

### sapling week 5/6 #7

Hi! I had a question about determining the most ordered to least ordered sample from the ΔS value. In this problem, I found all the ΔS values, and I thought the sample with the greatest ΔS value would be the most disordered and the sample with the smallest ΔS value would be the most ordered because ...
Fri Feb 12, 2021 7:53 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: ΔG =0 when solving for temperature
Replies: 2
Views: 24

### ΔG =0 when solving for temperature

Hi! I had a question about what Dr. Lavelle mentioned in lecture today. How are we able to set ΔG=0 when solving for the temperature when both the temperature and ΔG are unknown? The question was

At what temp is Br2(l)→Br2(g) spontaneous at 1atm? Given ΔH= 31 KJ/mol and ΔS= 93 J/KJ x mol

Thanks!
Fri Feb 12, 2021 7:47 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: ΔH and q
Replies: 6
Views: 53

### ΔH and q

Hi! I was wondering when you can use the q value as ΔH? Are they interchangeable or are there specific instances when you use different values for ΔH and q? Thanks!
Thu Feb 11, 2021 10:24 pm
Forum: Entropy Changes Due to Changes in Volume and Temperature
Topic: entropy at equilibrium
Replies: 3
Views: 15

### entropy at equilibrium

Hi! I was wondering if someone could explain why entropy is a maximum when the reaction is at equilibrium? How can you tell if a reaction is at equilibrium from just its entropy value? Thanks!
Thu Feb 11, 2021 10:21 pm
Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
Topic: reversible vs. irreversible reaction efficiency
Replies: 4
Views: 30

### reversible vs. irreversible reaction efficiency

Hi! I was wondering how a reversible reaction is more efficient if the work for a reversible reaction is greater? Thanks!
Fri Feb 05, 2021 2:42 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: ΔU=0 and entropy increase
Replies: 1
Views: 17

### ΔU=0 and entropy increase

Hi! I was wondering how the ΔU can be 0 if heat goes into a system? And how does this lead to an increase in entropy? Thanks!
Fri Feb 05, 2021 2:38 pm
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: irreversible reactions calculated as reversible
Replies: 2
Views: 12

### irreversible reactions calculated as reversible

Hi! Dr. Lavelle mentioned that systems are approximated as reversible in order to calculate the maximum work, so for irreversible reactions, is there a conversion calculation to do or do we just use the max work value? Thanks!
Fri Feb 05, 2021 2:29 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: energy replaced by heat
Replies: 3
Views: 31

### energy replaced by heat

Hi! I had a question about the equation q=-w. Dr. Lavelle mentioned in lecture that the energy lost in terms of work done by the system is replaced by heat, but I was wondering where the heat came from? Thanks!
Thu Feb 04, 2021 9:46 am
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: N value in degeneracy equation
Replies: 4
Views: 39

### N value in degeneracy equation

Hi! I was wondering how you know what to put as the base and what is the N value for the degeneracy equation? I was getting confused between the number of states and the possible positions. Thanks!
Wed Feb 03, 2021 12:45 am
Forum: Calculating Work of Expansion
Topic: integral equation
Replies: 7
Views: 53

### integral equation

Hi! I was wondering if someone could explain what type of system and reaction the equation w= - ∫P(dV) is used for? I am not really sure when to use this equation. Thanks!
Thu Jan 28, 2021 9:02 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Textbook Problem 4E.5a
Replies: 2
Views: 31

### Re: Textbook Problem 4E.5a

Hi! Make sure you are multiplying the bonds broken by 3 because it has 3 moles in the reactants. Also, make sure you use the resonance bond enthalpy for the benzene structure rather than 3 carbon single bonds and 3 carbon double bonds, so you would have 6 times the bond enthalpy of the resonance car...
Thu Jan 28, 2021 8:54 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Problem 6C.7 Help
Replies: 3
Views: 16

### Re: Problem 6C.7 Help

If the pKb is given, you can use the equation 14=pKa + pKb to find the pKa value. Hope this helps!
Thu Jan 28, 2021 8:27 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: sapling week 2 #10
Replies: 2
Views: 17

### sapling week 2 #10

Hi! I was wondering if someone could explain this question? I understand how to find if there are charged molecules or neutral molecules with an acid, but can someone explain how it works with a base? Do you have to convert to pKb and pOH and compare those values? Thanks!
Wed Jan 27, 2021 5:42 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Relationship between Work and Volume
Replies: 1
Views: 12

### Re: Relationship between Work and Volume

Hi! For this question I think you can use the equation we learned today in lecture, w=-PΔV. So if the change in volume is 0, the work would be zero. Hope this helps!
Wed Jan 27, 2021 5:40 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: mass in heat calculation
Replies: 3
Views: 12

### mass in heat calculation

Hi! I was wondering if you had a reaction with a certain amount (5g) of a substance and that was mixed with a certain amount of water (100ml), which value would you put in the q=mcΔt equation for mass? Thanks!
Fri Jan 22, 2021 6:44 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: standard reaction enthalpy vs standard enthalpy of formation [ENDORSED]
Replies: 2
Views: 39

### standard reaction enthalpy vs standard enthalpy of formation[ENDORSED]

Hi! I was wondering if someone could provide clarification on the difference between standard reaction enthalpy and standard enthalpy of formation? Is one for gas and the other for liquids? I wasn't sure what the difference in application was for these. Thanks!
Fri Jan 22, 2021 6:39 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: bonds broken and formed for bond enthalpy method [ENDORSED]
Replies: 2
Views: 24

### bonds broken and formed for bond enthalpy method[ENDORSED]

Hi! I was wondering how you know which bonds break and which bonds form for using the bond enthalpy to calculate ΔH? I was confused on how Dr. Lavelle said the double bond breaks but then you would have to add back the formation of a single bond between the two carbons in the example from lecture to...
Fri Jan 22, 2021 6:35 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: sulfuric acid deprotonation [ENDORSED]
Replies: 1
Views: 16

### sulfuric acid deprotonation[ENDORSED]

Hi! I had a question about polyprotonation mentioned in the textbook. I was confused as to why sulfuric acid (H2SO4) doesn't have a Ka value after its first deprotonation? There isn't a Ka value for when H2SO4 loses a proton and becomes HSO4- and I was wondering why? If someone could explain this, t...
Wed Jan 20, 2021 12:12 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Kw and aqueous solutions
Replies: 3
Views: 24

### Kw and aqueous solutions

Hi! I was wondering how the Kw value can be applied to any aqueous solution? Does it take the [H30+] and [OH-] from the product of the reaction of the aqueous solution? If anyone could provide clarification, that would be great! Thanks!
Wed Jan 20, 2021 12:09 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: amphoteric vs amphiprotic
Replies: 10
Views: 36

### amphoteric vs amphiprotic

Hi! I was wondering what the difference between amphoteric and amphiprotic is? I was wondering if there is a difference in the application of these two terms? I know water is amphiprotic, but does that mean it is also amphoteric? Can a compound be both or can it only be one? Thanks!
Fri Jan 15, 2021 9:50 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Kw equation
Replies: 9
Views: 106

### Re: Kw equation

Hi! Kw is basically the Kc value for water. 2 H20 dissociates into [H30+] and [OH-] and the equilibrium constant for this reaction is called Kw, and we know the value of this is always 1x10^-14. This value is important because when you use pKw (taking the -log of Kw), you get 14, which is the sum of...
Fri Jan 15, 2021 9:47 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Molar concentrations
Replies: 3
Views: 15

### Re: Molar concentrations

Hi! I agree with the other answer! For strong acids, you would not need to use an ICE table because the acid or base fully dissociates.
Fri Jan 15, 2021 9:45 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Non- water solvent
Replies: 7
Views: 54

### Non- water solvent

Hi! I had a question from today's lecture. I was wondering how you can tell which reactant is the solvent if it is not water? I know we are not supposed to include the solvent concentration in the Kc equation, so I was wondering how you know which one is the solvent if water is not a reactant? Thanks!
Wed Jan 13, 2021 10:38 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: pKw
Replies: 7
Views: 55

### Re: pKw

Hi! Adding on to this question, can the value Kw=10^-14 be used for reactions that don't have water? I thought I remembered in lecture that Dr. Lavelle used this value for the dissociation of Ba(OH)2. Can this Kw value also be used for reactions with H30+ and OH-? Thanks!
Wed Jan 13, 2021 10:33 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: pH and pKa
Replies: 6
Views: 33

### Re: pH and pKa

Hi! Adding on to this question, is pH associated with strong acids/bases and is pKa associated with weak acids/bases? I think I remember learning that if a reaction has a Ka/Kb value, that means it is a weak acid/base. If anyone could clarify, that would be great! Thanks!
Tue Jan 12, 2021 12:36 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Kw
Replies: 8
Views: 96

### Kw

Hi! I had a question about water and it's Kw value of 1x10^-14. Is water considered a strong acid/base? Since it is amphiprotic it can be an acid or a base, but since it has a Kw value, does that make it a weak acid/base? I remember Dr. Lavelle mentioning that only weak acids or bases have Ka values...
Fri Jan 08, 2021 7:09 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Inert Gas
Replies: 5
Views: 16

### Inert Gas

Hi! I had a question about the inert gas rule. I know Dr. Lavelle mentioned that the partial pressures of the reactants and products don't change when an inert gas is added, but what qualifies as an inert gas? Is is just a gas that is not in the reaction? Thanks!
Fri Jan 08, 2021 2:48 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE Table concentrations
Replies: 3
Views: 51

### ICE Table concentrations

Hi! I had a question about the quadratic that Dr. Lavelle mentioned in lecture. If there were two reactants that each had a different starting concentration and they had stoichiometric coefficients greater than 1, when using the K value to solve for x, this would make a polynomial greater than 2. Ho...
Fri Jan 08, 2021 10:12 am
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: Q>K
Replies: 10
Views: 52

### Q>K

Hi! I had a question about when the reaction quotient is larger than the equilibrium constant. I was wondering how this was possible because I figured once the reaction reached equilibrium the concentrations would remain the same. I wasn't sure how it would be possible to go beyond the equilibrium v...
Tue Jan 05, 2021 9:58 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Chemical Equilibrium Part 1B, #18
Replies: 4
Views: 31

### Re: Chemical Equilibrium Part 1B, #18

Hi! So for this problem I don't think you need to use PV=nRT. You can calculate the equilibrium constant by using partial pressures too, which is what is given in this problem. You would just need to balance the reaction first. Hope this helps!
Tue Jan 05, 2021 9:55 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: change in pressure
Replies: 8
Views: 93

### change in pressure

Hi! I was wondering which direction the reaction would shift (or if it would shift) if the pressure was changed but there are the same number of moles of gas on both sides? Thanks!
Fri Dec 11, 2020 11:31 pm
Forum: Identifying Acidic & Basic Salts
Topic: 6D.11 part e and f
Replies: 2
Views: 50

### Re: 6D.11 part e and f

Hi! So the they used the ions Al3+ and Cu2+ because the other ions (Cl- and NO3-) are spectator ions are they are derived from strong acids so they wouldn't affect the pH of the solution. You can break up the salt into its ions and decide if they are derived from strong or weak acids and bases. If t...
Fri Dec 11, 2020 11:23 pm
Forum: Hybridization
Topic: Today's Review Video: CO2
Replies: 2
Views: 50

### Re: Today's Review Video: CO2

Hi! I think hybridization only applies to atoms with regions of electron density around it (bonds to other atoms and lone pairs), so it is not necessarily referring to the actual bond between the atoms, rather the number of electron density regions around an atom. Hope this helps!
Thu Dec 10, 2020 1:23 am
Forum: Conjugate Acids & Bases
Topic: Weak Acid and Weak Base
Replies: 2
Views: 27

### Re: Weak Acid and Weak Base

I think you would determine if the solution is acidic or basic based on the amount of H30+ ions and OH- ions, so you might need more information to determine which one (acid or base) dissociates more.
Thu Dec 10, 2020 1:18 am
Forum: Polyprotic Acids & Bases
Topic: How many protons released for Polyprotics?
Replies: 2
Views: 55

### Re: How many protons released for Polyprotics?

For this example, since it has 3 H atoms, it can donate up to 3 protons, but each time it donates one proton, the molecule gets a greater negative charge, so it is harder to pull more protons away.
Mon Dec 07, 2020 11:11 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: carbonate and sulfate ligands
Replies: 1
Views: 33

### carbonate and sulfate ligands

Hi! I was wondering if the carbonate and sulfate ligands (carbonato and sulfato) are mono dentate or bidentate? If they are bidentate, are they chelating ligands? How do you identify if the bonded atoms on the ligand are too far away to be a chelating ligand? Thanks!
Fri Dec 04, 2020 8:28 pm
Forum: Sigma & Pi Bonds
Topic: sigma and pi bonds for benzene molecule
Replies: 3
Views: 68

### sigma and pi bonds for benzene molecule

Hi! I had a question about the number of sigma and pi bonds in a benzene molecule (C6H6). Since the molecule has a ring of carbons in a hexagon shape with 3 double bonds, would this mean there are 6 sigma bonds and 3 pi bonds in the carbon ring? I wasn't sure how this would work since technically al...
Fri Dec 04, 2020 8:23 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Coordination Number for square planar molecule
Replies: 3
Views: 51

### Coordination Number for square planar molecule

Hi! I was wondering why a square planar molecule had a coordination number of 4? Since it has 6 electron groups (4 bonded atoms and 2 lone pairs) I thought the coordination number would be 6. Thanks!
Wed Dec 02, 2020 7:05 pm
Forum: Properties & Structures of Inorganic & Organic Acids
Topic: Acid strength and bond length
Replies: 11
Views: 160

### Acid strength and bond length

Hi! I was wondering what the relationship between bond length and acid strength is? In the example of HCl and HBr, since HBr's bond is longer, I was wondering which one is the stronger acid and how to tell? Thank you!
Tue Dec 01, 2020 10:32 pm
Forum: Hybridization
Topic: when to use hybridization
Replies: 2
Views: 56

### when to use hybridization

Hi! I was wondering how to know which molecules use a combination of hybridized and unhybridized orbitals? I remember there was an example that had some electrons in the 2sp3 orbitals and then it also had electrons move up to the 2p orbital. I was wondering how you know to use this format? Here is a...
Mon Nov 30, 2020 10:29 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: trigonal bipyramidal electron geometry
Replies: 2
Views: 49

### trigonal bipyramidal electron geometry

Hi! I was wondering why the lone pairs in a molecule with trigonal bipyramidal electron geometry would go in the equatorial position? I thought the axial positions would have the greatest distance apart because of the lone pair repulsion. Thanks!
Sat Nov 28, 2020 3:27 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: t-shaped structure
Replies: 1
Views: 33

### t-shaped structure

Hi! I was wondering if the 3 bonded atoms in a figure with t-shaped geometry are on the same plane? Or are the 3 bonded atoms in a pyramidal formation? I was wondering this to help figure out the angles between the atoms. Thanks!
Sat Nov 28, 2020 3:21 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: delocalized pi bond
Replies: 8
Views: 113

### delocalized pi bond

Hi! I was wondering what the difference between a pi bond and a delocalized pi bond is? Thanks!
Wed Nov 25, 2020 12:05 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: coordinate covalent bond angle
Replies: 1
Views: 56

### coordinate covalent bond angle

Hi! I had a question from lecture 24 today. In the example with Cl-, it has 3 sets of lone pairs and and one of them form the coordinate covalent bond. What happens to the bond angle between the other 2 lone pairs and the lone pair that was bonded? Since the electron repulsion is lower for bonds tha...
Mon Nov 23, 2020 8:28 pm
Forum: Hybridization
Topic: Carbon double bond
Replies: 3
Views: 50

### Carbon double bond

Hi! I had a question about something Dr. Lavelle mentioned in lecture. Whenever there is a double bond on C, does that mean the whole molecule is on one plane? I think he said the double bond locks the C into the location, so are all the bonded atoms also on the same plane? Thanks!
Mon Nov 23, 2020 8:26 pm
Forum: Hybridization
Topic: Hybridization Application
Replies: 2
Views: 24

### Hybridization Application

Hi! I was wondering if hybridization is used in every molecule? How do you distinguish when it is used and when it is not? Thanks!
Sat Nov 21, 2020 6:04 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: comparing bonds and lone pairs
Replies: 5
Views: 71

### Re: comparing bonds and lone pairs

Hi! So I think you would look at the repulsion strength. Lone pair- lone pair repulsion is the greatest, then lone pair- bonding pair, then bonding pair-bonding pair repulsion is the weakest. So if you look at an angle between two lone pairs, that would be the biggest, and then an angle between two ...
Sat Nov 21, 2020 6:01 pm
Forum: Hybridization
Topic: Double bonds structures
Replies: 5
Views: 91

### Double bonds structures

Hi! I had a question about something Dr. Lavelle mentioned in lecture, that if an atom has a double bond, then it cannot move around and it is locked into a position by these bonds. I was wondering how this applies to structures with resonance and if the electrons are delocalized? Thanks!
Thu Nov 19, 2020 11:31 pm
Forum: Bond Lengths & Energies
Topic: Bond Strength in DNA
Replies: 12
Views: 149

### Bond Strength in DNA

Hi! I had a question about AT and GC pairs in DNA. Since AT base pairs have only 2 hydrogen-bonding sites and GC has 3 hydrogen bonding sites, is GC stronger? Or are the bond strengths of AT and GC pretty comparable because they both are able to hydrogen bond? I was wondering if that 3rd h-bond in G...
Wed Nov 18, 2020 11:41 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR Notation
Replies: 3
Views: 29

### VSEPR Notation

Hi! I had a question about the AXE notation used in VSEPR. I understood that A is the central atom and X is the bonded atom, but what if the bonded atoms are not all the same? Is there a way to distinguish these different molecules in the notation? EX: CHCl3- would this just be AX4 or is there a way...
Wed Nov 18, 2020 11:22 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: Electron density in VSEPR models
Replies: 4
Views: 37

### Electron density in VSEPR models

Hi! I had a question about the different regions of electron densities in the VSEPR model. Does this model assume that lone pairs and bonded atoms have the same electron density? Or do the lone pairs have a bigger electron cloud than the bonded atoms? I was wondering this because Dr. Lavelle mention...
Fri Nov 13, 2020 11:04 pm
Forum: Dipole Moments
Topic: Interaction potential energy
Replies: 2
Views: 34

### Interaction potential energy

Hi! So Dr. Lavelle mentioned that the interaction potential energy is always negative, and I was wondering why we know that that is always an attractive force? Thanks!
Fri Nov 13, 2020 10:58 pm
Forum: Resonance Structures
Topic: Resonance hybrid of molecules
Replies: 2
Views: 28

### Resonance hybrid of molecules

Hi! I was wondering what exactly the resonance hybrid is and how you know what structure contributes to the resonance hybrid? Thanks!
Wed Nov 11, 2020 9:17 pm
Forum: Dipole Moments
Topic: Electron distortion
Replies: 1
Views: 16

### Electron distortion

Hi! I had a question from lecture today about electron distortion. Dr. Lavelle mentioned that the level of electron distortion determines the physical state of the molecule (solid, liquid, gas). I was wondering what exactly this relationship is? Like how electron distortion correlates to what the ph...
Tue Nov 10, 2020 9:46 pm
Forum: Octet Exceptions
Topic: electron deficiency
Replies: 2
Views: 24

### electron deficiency

Hi! I had a question about something Dr. Lavelle mentioned in lecture about boron and aluminum being electron deficient. Is this in terms of the ion forms and also what does it mean in terms of accepting electrons and reactivity? Thanks!
Mon Nov 09, 2020 10:11 pm
Forum: Bond Lengths & Energies
Topic: bond length for different compounds
Replies: 3
Views: 26

### bond length for different compounds

Hi! I had a question on how to compare bond lengths of different molecules. I understand that in an example like HF and HI, HF has a much smaller bond length. However, how would you compare the bond length of compounds such as HF and CO? Thanks!
Thu Nov 05, 2020 11:47 pm
Forum: Formal Charge and Oxidation Numbers
Topic: formal charge and stability
Replies: 8
Views: 59

### formal charge and stability

Hi! I had a question about formal charge and rewriting structures. I think Dr. Lavelle mentioned that if a structure can be redrawn so the atoms in the compound have a formal charge of 0, that means the compound is more stable? Would we check every time one of the atoms has a formal charge that is n...
Thu Nov 05, 2020 11:43 pm
Forum: Ionic & Covalent Bonds
Topic: resonance structures
Replies: 2
Views: 22

### Re: resonance structures

I think quadruple bonds may be unlikely because that would mean all the electrons between two atoms are shared. It would mean there are 8 electrons for each element already, so it wouldn't be able to have any lone pair electrons or be bonded to other atoms unless it was in n=3 or higher where it can...
Wed Nov 04, 2020 11:17 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Topic 1E. 17 Problem
Replies: 2
Views: 31

### Re: Topic 1E. 17 Problem

Hi! So when you are trying to find which orbital an electron will be removed from to form a +1 ion, you look at the highest energy level and type of orbital that the electrons of that atom occupy. So for Mn, since the highest level that the electrons occupy is 4s, an electron will be removed from th...
Wed Nov 04, 2020 11:02 pm
Forum: Lewis Structures
Topic: First 3 elements' octet
Replies: 4
Views: 37

### First 3 elements' octet

Hi! I had a question from Dr. Lavelle's lecture today. He mentioned that the first 3 elements (H, He, Li) don't have an octet in their lewis structures. I was wondering why that is? Thank you!
Mon Nov 02, 2020 6:42 pm
Forum: Resonance Structures
Topic: Resonance and double bonds
Replies: 4
Views: 29

### Resonance and double bonds

Hi! I had a question from lecture today about when resonance is occurring. Does a structure have resonance whenever there is a double or triple bond? Thanks!
Thu Oct 29, 2020 9:23 pm
Forum: Trends in The Periodic Table
Topic: Electron-electron repulsion
Replies: 5
Views: 71

### Electron-electron repulsion

Hi! Could someone explain when electron-electron repulsion is relevant? I've heard Dr. Lavelle mention it a few times in lecture but I'm not super clear as to when this topic is applied to a periodic trend. Thanks!
Thu Oct 29, 2020 9:21 pm
Forum: Trends in The Periodic Table
Topic: Positive and negative electron affinity
Replies: 2
Views: 50

### Positive and negative electron affinity

Hi! Could someone explain what positive and negative electron affinity means? I'm having some difficulty understanding these two in relation to the definition of electron affinity. Thank you!
Thu Oct 29, 2020 9:06 pm
Forum: Properties of Electrons
Topic: Electron Energy
Replies: 2
Views: 59

### Re: Electron Energy

I think we can also take into consideration the deBroglie equation which relates wavelength and velocity: λ=h/mv
If a question provides velocity and asks to find wavelength, this could be a good equation to use!
Wed Oct 28, 2020 8:24 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Rydberg Equation question (sapling hw2 #12)
Replies: 3
Views: 50

### Rydberg Equation question (sapling hw2 #12)

Hi! I had a question about sapling HW2 #12. In the solution, the rydberg equation was used but for the (1/n^2- 1/n^2) part, which energy level comes first? If the electron is moving from n=3 to n=1, which one to do you put for n1 and n2? Thanks!
Wed Oct 28, 2020 7:45 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: electron configuration for p orbital
Replies: 2
Views: 18

### electron configuration for p orbital

Hi! I wanted some clarification on writing the electron configuration in the p orbital with 4 or more electrons in that orbital. Dr. Lavelle mentioned that we're supposed to write 1s2,2s2,2px1,2py1,2pz1 and so on, so if this was for Oxygen, would it be written like 1s2, 2s2, 2px2, 2py1, 2pz1? Would ...
Fri Oct 23, 2020 3:31 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Angular Momentum Quantum number
Replies: 3
Views: 23

### Angular Momentum Quantum number

Hi! I had a question about the angular momentum quantum number (l) and the associated orbitals. I think Dr. Lavelle mentioned that the values for l (0,1,2,3) are associated with the orbitals (s,p,d,f), but I was wondering what happens if the value of l is greater than 3? Thanks!
Fri Oct 23, 2020 3:27 pm
Forum: Trends in The Periodic Table
Topic: Shielding Effect
Replies: 2
Views: 36

### Shielding Effect

Hi! I had a conceptual question about the shielding effect. So since the shielding is caused by the energy shells and how the outer electrons don't feel the whole nuclear charge because the lower electrons are blocking it, does this assume that the electrons are in line with each other in the shells...
Thu Oct 22, 2020 11:25 pm
Forum: Trends in The Periodic Table
Topic: Sapling Hw 2 #20
Replies: 3
Views: 68

### Sapling Hw 2 #20

Upon ionization, oxygen is relieved on electron-electron repulsions.
Could someone explain this concept? Thanks!
Thu Oct 22, 2020 11:18 pm
Forum: DeBroglie Equation
Topic: Sapling Hw 2 #19
Replies: 10
Views: 157

### Sapling Hw 2 #19

Hi! I had a question about #19 on sapling hw 2. The question reads: What would the speed of each particle be if it had the same wavelength as a photon of yellow light (575.0 nm)? And several masses are given. I thought I would use the deBroglie equation and solve for velocity, but it doesn't seem to...
Tue Oct 20, 2020 10:38 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Electromagnetic radiation and associated energy levels
Replies: 4
Views: 47

### Electromagnetic radiation and associated energy levels

Hi! I had a question about what energy levels were associated with which parts of the electromagnetic spectrum. I think Dr. Lavelle mentioned that the UV region was n=1 and visible light was n=2, and what is the the association for the infrared region? Would it be that any energy level changes to le...
Mon Oct 19, 2020 11:48 am
Forum: DeBroglie Equation
Topic: Wavelike and particle like behavior
Replies: 3
Views: 50

### Wavelike and particle like behavior

Hi! I had a question regarding when wavelike and particle like behavior is detectable. So Dr. Lavelle mentioned that wavelike behavior is only detectable if the number is greater than 10^-15. Is particle like behavior always detectable? Also is there a maximum for when wavelike behavior can be detec...
Thu Oct 15, 2020 5:53 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Kinetic energy per mole of electrons
Replies: 2
Views: 55

### Kinetic energy per mole of electrons

Hi! when you have the uncertainty in kinetic energy, how do you find the uncertainty in kinetic energy per mole of electrons? Thanks!
Wed Oct 14, 2020 10:09 pm
Forum: DeBroglie Equation
Topic: equation units help
Replies: 2
Views: 49

### equation units help

Hi! If a problem gives the mass in kg and the velocity in (m/s), do you have to convert anything before solving for the wavelength? Thanks!
Wed Oct 14, 2020 10:45 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: atomic spectroscopy question
Replies: 2
Views: 62

### atomic spectroscopy question

Hello! I had a question about the spectroscopic experiment discussed in lecture. When light energy doesn’t match the energy difference between 2 energy levels, how come it passes through rather than being reflected back? Thank you!
Mon Oct 12, 2020 11:16 pm
Forum: Properties of Electrons
Topic: Kinetic energy of electrons
Replies: 3
Views: 50

### Kinetic energy of electrons

Hi! I was wondering how you would calculate the kinetic energy of an electron that has been ejected off a metal surface by a light if you're only given the velocity? I tried to use the 1/2mv^2 but I wasn't sure what mass to use. Thanks!
Sat Oct 10, 2020 5:02 pm
Forum: Empirical & Molecular Formulas
Topic: Sapling Hw 1 #10
Replies: 5
Views: 49

### Sapling Hw 1 #10

Hi! I was wondering how you would write the chemical equation for this question? Thanks! Consider the nucleophilic addition reaction of 2‑butanone with excess propyl magnesiumbromide, made in situ by reacting 1‑bromopropane with metallic magnesium, to make 3‑methyl‑3‑hexanol. A reaction was performe...
Fri Oct 09, 2020 12:30 pm
Forum: Balancing Chemical Reactions
Topic: Combining Atoms
Replies: 7
Views: 144

### Re: Combining Atoms

Often times, if the element has different charges like Cu, it will tell you copper (II) oxide, so you know to use the copper with the 2+ charge.
Thu Oct 08, 2020 11:00 pm
Forum: Empirical & Molecular Formulas
Topic: Arrangement of elements/polyatomic ions
Replies: 2
Views: 45

### Re: Arrangement of elements/polyatomic ions

Yes! And if the compound is not a hydrocarbon, the metal comes first and the nonmetal comes second.
Wed Oct 07, 2020 11:26 pm
Forum: Empirical & Molecular Formulas
Topic: L 35
Replies: 1
Views: 45

### L 35

For this question, do you use the first two equations for anything?

Thanks!